Climate change and the future of the Great Barrier Reef. Ove Hoegh - PowerPoint PPT Presentation

Climate change and the future of the Great Barrier Reef. Ove Hoegh ‐ Guldberg Global Change Institute ARC Centre for Excellence for Coral Reef Studies for Coral Reef Studies The University of Queensland www.coralreefecosystems.org www.climateshifts.org

1975 1975 1981 1981 2004 2004 M lti l Multiple ‐ use Gold standard

Andrew Elliott – May 24 1994 Photos compiled by David Wachenfeld, Great Barrier Reef Marine Park Authority

Great Barrier Reef: Great Barrier Reef: Is coral cover decreasing? Is coral cover decreasing? Changes in hard coral cover from Changes in hard coral cover from 1980-83 to 2000-2003 Bruno and Selig 2007, PLoS ONE 2 Bellwood et al 2004 Nature 429: 827-833 Sweatman et al. 2010 - Changes in hard coral cover on the GBR - (fixed sites) 1993-2007 ?

M. Devlin, James Cook University & RRRC 2011 McCulloch et al. 2003 (Nature, 421: 727 ‐ 730

Mass coral bleaching GBR 2006 STRESS STRESS STRESS

Mass Bleaching Events H H Hoegh Hoegh ‐ Guldberg (1995) h h G ldb G ldb Guldberg (1995) (1995) (1995) Extensive experimental evidence

Small changes in sea temperature explained patterns of mass bleaching and mortality 1998 1998 2002 2002  T anomalies >50% >50% 16% of the world’s  T X exposure time corals died in 1998 l di d i 1998 1998: DHW Bleaching Severe Bleaching Mass Mortality

Sea temperatures are Australian Bureau of Meteorology increasing steadily within the Coral Sea. While we have been lucky so far, other regions like the , g Caribbean have not Worst bleaching ever Caribbean – predictive tools indicate rising stress levels Spillman et al. 2011 (American Meteorological Society)

2010 – the hottest year on the instrument record Global temperature Tobago, Caribbean 2010 Hansen, et al. 2010 Rev. Geophys. , accepted. accepted. Summer DHW values in 2010

Great Barrier Reef E trapolating from the past 20 ears to the f t re Extrapolating from the past 20 years to the future ? Threshold temperature – above which bleaching and mortality occur WHAT DOES THE FUTURE HOLD? Hoegh-Guldberg (1999) – Trajectories based on IS92A (doubling of CO 2 by 2100)

Crucial question: Could corals evolve fast enough to keep up with climate change? Issues Issues Issues Issues IF SO, THEN NO PROBLEM! , ure (oC) • Corals tend to have • Corals tend to have Physiological threshold Temperatu – Long generation times (5 ‐ 100 years) – Long generation times (5 ‐ 100 years) – Low diversity populations – Low diversity populations Sea T • Not bacteria or even Drosophila! • Not bacteria or even Drosophila! • Evolution likely to be slow rather than fast • Evolution likely to be slow rather than fast Hoegh ‐ Guldberg (1999)

Could corals migrate their Could corals migrate their way out of trouble? way out of trouble? 30 o C 27 o C Coral reefs would have to move at the rate of at least 15 km per year!

Swapping your symbionts to increase your temperature tolerance? Great idea: any evidence? Great idea: any evidence? Great idea: any evidence? Great idea: any evidence? Completely new No change: No change: symbiont Stress Repopulate established ‐ Michael Stat Michael Stat K’le Gomez ‐ Cabrera K’le Gomez ‐ Cabrera higher temperature Eugenia Sampayo Eugenia Sampayo tolerance Bleach How many more??? How many more???

Co ‐ evolution of host and symbiont Between species Within species otypye biont geno Deep Symb Shallow Shallow Host genotype Seriatopra hystrix Li ard Island Lizard Island Bongaerts P, Ridgway T, Riginos C, Englebert N, Sampayo E Vermeulen Sampayo E, Vermeulen F, Hoegh-Guldberg O (2010) LaJeunesse, Hoegh ‐ Guldberg, Schmidt, Fitt (2003)

Hoegh ‐ Guldberg et al. 2007 Science Ocean Acidification 2 ‐ CO 3 ns ns 3 Fraction Fraction Log F Log F 2 ‐ CO 3 7.6 7.8 8.0 8.2 7.6 7.8 8.0 8.2 pH pH K. Anthony

Today Paleo ‐ reconstructions (2) from boron isotopes in foraminifera atmosphere–ocean– sediment carbon cycling model Pelejero, Calvo and Hoegh ‐ Guldberg (2010)

Impacts on coral calcification: Kleypas and Langdon (2006) All negative g 1, 4, 5 => adjusted using CO 2 Range per unit decrease in aragonite saturation: 5 ‐ 38% decrease (~ 17%) Note: 1 unit decrease in aragonite g saturation ~ 140 ppm increase in atm CO 2 Double CO2 ~ 280 ppm

Is a decrease of 5 ‐ 38% with a doubling of CO2 going to change m ch? of CO2 going to change much? Coral growth Reef accretion ee acc e o (10 ‐ 300 mm/year) Reef growth (1 3 mm/year) (1 ‐ 3 mm/year) Davies (1985) n icatio icatio sion sion Calcifi Calcifi Ero Ero Carbonate balance of reefs is all important C

Ocean acidification and aragonite saturation Ω Ω arag arag 3.3 (limit for carbonate Hoegh-Guldberg et al. 2007 (Science Vol 318) coral reefs)

Other factors Other factors Storm damage Storm damage Coastal run Coastal run ‐ Coasta Coasta u u ‐ off off o (esp esp after drought) after drought)

Annual calcification rate of 328 long ‐ lived corals 1990 1990 15% decrease since 1990 (no other in 400 yrs of record) De’ath et al. 2009

$6 $6 $6.5 billion/year $6.5 billion/year billi billi / / 63,000 jobs 63,000 jobs 1 million species 1 million species 1 million species 1 million species

Hoegh ‐ ‐ Guldbe erg et a al. 2007 Scienc e, v. 31 8

The future of coral reefs? The future of coral reefs? Hoegh ‐ Guldberg et al. 2007 (Science) g g ( ) 387 ppm 450 ppm >500 ppm +1.0 o C +2 o C > +2 o C What does this mean for GBR industry and communities?

Tourism plays a major role in earnings of five Great Barrier Reef regions (differ in relative importance) Barrier Reef regions (differ in relative importance) 83% of economy depends on depends on reef ‐ related earnings What if the GBR were no longer were no longer Hoegh ‐ Guldberg and Hoegh ‐ Guldberg (2004) ‘great’? www. wwf .org.au/publications/ ClimateChange GBR.pdf

What will it take What will it take t t to save the GBR? to save the GBR? th th GBR? GBR?

The significance of 450 ppm and the 2°C guardrail? d th 2°C d il? Implications: 1 000 GT f C 1,000 GT of Carbon b dioxide left to emit (emit 30 ‐ 40 GT per year at present) Clock started in GBR gone? g 2000: only 700 GT GBR increasingly left to emit damaged by  T, pH Meinshausen et al. 2009 (Nature 458, 1158 ‐ 1162)

700 GT CO 2 left to emit 2 (for a 60% chance of remaining below 450 ppm)

Is still ‘Great’ Vast economic engine Vast economic engine Globally valued 1. Extreme climate change threat 1 E t li t h th t 2. Reef is not adapting fast enough 3 3. Major risk to people and industry Major risk to people and industry 4. 450 ppm and +2°C guard ‐ rail critical to GBR survival 5. Managing local factors will get more not less important